In recent years, the provision of mobile phone services in a service area by a small base station called a femtocell has been considered. In this scheme, generally, a femtocell gateway (FGW) and a femtocell access point (femto AP) are connected using an internet protocol (IP) broadband line such as an asymmetric digital subscriber line (ADSL) and fiber to the home (FTTH).
Various services to be provided by femtocell service are under consideration, such as the provision of a signal reception environment better than that of a macrocell, a high-speed data communication environment achieved as a result of the better reception environment, and exclusive utilization of a frequency by a user to improve efficiency in frequency utilization as well as lower flat rate service fees charged by mobile phone carriers.
In an environment where a broadband line is available, by a mere connection of a femto AP, femtocell services can be enjoyed. The femto AP is installed at the residence of a user subscribing to the service. Consequently, deregulation in the mobile phone industry is expected, thereby enabling users to freely change the installation place or turn on and off the power of the femto AP.
In addition to providing services having the advantages above, a femtocell scheme can realize a communication link with information terminal home appliances. For example, typically, communication between a personal computer (PC) and a mobile phone is achieved by the use of a memory card or a dedicated communication cable with software as a communication medium. However, operations such as inserting and removing the memory card or communication cable are very troublesome for the user.
On average, every two years, users newly purchase mobile phones to replace existing ones. To transfer files from an existing mobile phone to a newly purchased mobile phone, a user first stores the files in the existing mobile phone on a PC at home. A technique to simplify communication between a mobile phone and a PC is disclosed in Japanese Laid-Open Patent Publication No. 2007-282255.
As a general communication method between a mobile phone and a PC, WiFi (a wireless local area network (LAN) technology) may be considered and a 3GPP mobile terminal equipped with WiFi is actually available. However, such dual terminals have problems in terms of power consumption and cost. As a means to address these problems, wireless communication schemes supported by femtocells are limited to mobile communication schemes (for example, 3GPP).
For the femtocell service, communication at a residence, achieved through the femto AP installed at the residence is assumed between a mobile communication network and a mobile terminal, whereas communication between a PC and a mobile terminal is not assumed basically. Therefore, at a residence, the transmission of a packet from a PC to a mobile terminal is difficult.
The problem is specifically explained. In a regular femtocell service, an address for use in a mobile communication network (mobile communication network address) is given to a mobile terminal each time data communication with respect to the mobile terminal is requested. Because of resource constraints, in mobile communication, an IP address is usually released after the communication has finished. Therefore, when packet transmission from a PC to a mobile terminal is attempted, the current mobile communication network address assigned to the mobile terminal cannot be obtained by the PC.
Even when the PC can obtain the mobile communication network address of the mobile terminal, if the mobile communication network address changes thereafter, the PC transmits a packet having an invalid address and thus, cannot transmit the packet properly to the mobile terminal. Hence, when the mobile communication network address of a mobile terminal changes, communication between a PC and the mobile terminal is difficult.
Therefore, for example, it becomes difficult to achieve Plug and Play (PnP) of the mobile terminal with respect to a local network that is a Universal Plug and Play (UPnP) network. Moreover, when the mobile terminal receives a call, an IP address is assigned by calling the mobile terminal, and therefore, a problem occurs if the IP address retained by the caller is not the IP address recorded in UPnP.